arXiv subjects

E. V. Bugaev

Publications and source records attributed to E. V. Bugaev.

At least 37 records · Page 2Linked to original sources

arXiv2003

Photonuclear interaction of high energy muons and tau-leptons

General formalism for a two-component description of the inelastic lepton-nucleon scattering in the diffractive region is proposed. Nonperturbative contribution to electromagnetic structure functions of a nucleon is described by the modified generalized vector dominance model containing special cut-off factors restricting the phase volume of initial qq-pairs of virtual photon's fluctuations. Perturbative QCD contribution is described by the phenomenological model suggested (in nonunitarized form) by Forshaw, Kerley and Shaw. Formulae needed for a numerical calculation of photonuclear cross sections integrated over Q^2 are presented. It is argued that in a case of the photonuclear cross sections at superhigh energies of leptons (E>=10^6GeV), integrated over Q^2, the following two-component scheme is good enough: the nonperturbative contribution is approximated by the old parameterization of Bezrukov and Bugaev, and perturbative one is described by the model of Forshaw, Kerley and Shaw with parameters determined from DESY data. Corresponding results of numerical calculations of the perturbative part, for the cases of muon and tau-lepton scattering at superhigh energies, are given.

hep-ph↗

arXiv2002

Cosmological constraints from evaporations of primordial black holes

The formula for the initial mass spectrum of primordial black holes (PBHs), which can be used for a general case of the scale dependent spectral index, and for a wide class of models of the gravitational collapse, is derived. The derivation is based on the Press and Schechter formalism. The comparative analysis of different types of initial mass spectra used in concrete calculations is carried out. It is shown that densities of background radiations ($ν$, $γ$) from PBH evaporations depend rather strongly on a type of the gravitational collapse and on a taking into account the spread of horizon masses at which PBHs can form. Constraints on parameters of the primordial density perturbation amplitudes based on PBH evaporation processes and on atmospheric and solar neutrino data are obtained.

astro-ph↗

arXiv2002

Neutrino background spectra from primordial black hole evaporations: dependence on the initial mass spectrum

Comparative analysis of different types of initial mass spectra of primordial black holes (PBHs) is carried out. It is assumed that primordial density fluctuations have power law spectrum and the spectral index is constant throughout all scales. It is shown that densities of background radiations (neutrinos, gamma-quanta) from PBH evaporations strongly depend on the type of gravitational collapse and on the way of taking into account the spread of horizon masses at which PBHs can form. Constraints on spectral index values based on PBH evaporation process and on atmospheric and solar neutrino data are obtained.

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arXiv2002

Possibility of parametrization of atmospheric muon angular flux using underwater data

We present the formula for angular distribution of integral flux of conventional ($π, K$) muons deep under water taking into account the sphericity of the atmosphere and fluctuations of muon energy losses.The accuracy of this formula for various sea level muon spectra is discussed. The possibility of reconstructing two parameters of sea level spectrum by fitting measured underwater angular intensity is shown for Baikal Neutrino Telescope NT--36 experimental data.

hep-ph↗

arXiv2002

Accuracy of muon transport simulation

Chain of calculations which have to be performed to predict any kind of signal in a deep underwater/ice neutrino detector necessarily includes the lepton propagation through thick layers of matter, as neutrino can be observed only by means of leptons (muons, first of all, due to their large ranges) that are generated in $νN \to l N$ interactions. Thus, the muon propagation plays a key role when analyzing data and it is important to understand clearly how transportation part of simulation chain contributes to total inaccuracy of final results. Here we consider sources of uncertainties that appear in Monte Carlo algorithms for simulation of muon transport. The trivial but effective test is proposed to measure the propagation algorithm accuracy. The test is applied to three MC muon transport codes (PROPMU, MUSIC, MUM) and results are reported.

hep-ph↗

arXiv2001

Baryon asymmetry of the Universe from evaporation of primordial black holes

The process of baryogenesis through the evaporation of black holes formed at the end of inflation phase is considered. The increase of black hole mass due to accretion from the surrounding radiation after the reheating is taken into account. It is shown that the influence of the accretion on the baryogenesis is important only in the case when the initial values of black hole mass are larger than $\sim 10^{4}{g}$. The behavior of calculated baryon asymmetry, as a function of model parameters, is studied.

astro-ph↗

arXiv2001

Extragalactic neutrino background from PBHs evaporation

We calculated the energy spectra and the fluxes of electron neutrinos in extragalactic space emitted in the process of the evaporation of primordial black holes (PBHs) in the early universe. It was assumed that PBHs are formed by a blue power-law spectrum of primordial density fluctuations. In the calculations of neutrino spectra the spectral index of density fluctuations and the reheating temperature were used as free parameters. The absorption of neutrinos during propagation in the space was taken into account. We obtained the bounds on the spectral index assuming validity of the standard picture of gravitational collapse and using the available data of several experiments with atmospheric and solar neutrinos. The comparison of our results with the previous constraints (which had been obtained using diffuse photon background data) shows that such bounds are quite sensitive to an assumed form of the initial PBH mass function.

astro-ph↗

arXiv2001

MUM: flexible precise Monte Carlo algorithm for muon propagation through thick layers of matter

We present a new Monte Carlo muon propagation algorithm MUM (MUons+Medium) which possesses some advantages over analogous algorithms presently in use. The most important features of algorithm are described. Results on the test for accuracy of treatment the muon energy loss with MUM are presented and analyzed. It is evaluated to be of 0.002 or better, depending upon simulation parameters. Contributions of different simplifications which are applied at Monte Carlo muon transportation to the resulting error are considered and ranked. It is shown that when simulating muon propagation through medium it is quite enough to account only for fluctuations in radiative energy loss with fraction of energy lost being as large as 0.05 -- 0.1. Selected results obtained with MUM are given and compared with ones from other algorithms.

hep-ph↗

arXiv2001

Analytical description of muon distributions at large depths

The analytical expression for integral energy spectra and zenith angle distributions of atmospheric muons at large depths is derived. Fluctuations of muon energy losses are described using the parametrized correction factor. The fitting formula for the sea level muon spectrum at different zenith angles for spherical atmosphere is proposed. The concrete calculations for pure water are presented.

hep-ph↗

arXiv2001

Precise parametrizations of muon energy losses in water

The description of muon propagation through large depths of matter, based on a concept of the correction factor, is proposed. The results of Monte-Carlo calculations of this correction factor are presented. The parametrizations for continuous energy loss coefficients, valid in the broad interval of muon energies, and for the correction factor are given. The concrete calculations for pure water are presented.

hep-ph↗

arXiv2001

MUM: flexible precise algorithm for the muon propagation

We present a new muon propagation Monte Carlo FORTRAN code MUM (MUons+Medium) which possesses some advantages over analogous codes presently in use. The most important features of the algorithm are described. Data on the test for algorithm accuracy are presented. Contributions of different sources to the resulting error of simulation are considered. Selected results obtained with MUM are given and compared with ones from other codes.

hep-ph↗

arXiv2001

On the parametrization of atmospheric muon angular flux underwater

The analytical expression for angular integral flux of atmospheric muons in matter with the explicit relation of its parameters with those of the sea level spectrum is obtained. The fitting formula for the sea level muon spectrum at different zenith angles for spherical atmosphere is proposed. The concrete calculations for pure water are presented. Fluctuations of muon energy losses are taken into account by means of parametrized correction factor calculated using survival probabilities resulted from Monte Carlo simulations. Parametrizations of all continuous energy losses are obtained with using the most recent expressions for muon interaction cross-sections. The corresponding parametrization errors and field of method application are comprehensively discussed. The proposed formulae could be useful primarily for experimentalists processing data of arrays located deep under water or under ice.

hep-ph↗

arXiv2000

Constraints on diffuse neutrino background from primordial black holes

We calculated the energy spectra and the fluxes of electron neutrino emitted in the process of evaporation of primordial black holes (PBHs) in the early universe. It was assumed that PBHs are formed by a blue power-law spectrum of primordial density fluctuations. We obtained the bounds on the spectral index of density fluctuations assuming validity of the standard picture of gravitational collapse and using the available data of several experiments with atmospheric and solar neutrinos. The comparison of our results with the previous constraints (which had been obtained using diffuse photon background data) shows that such bounds are quite sensitive to an assumed form of the initial PBH mass function.

astro-ph↗

arXiv2000

Simulation accuracy of long range muon propagation in medium: analysis of error sources

Knowledge of atmospheric muon flux intensity at large depths is extremely important for neutrino telescopes located deep under ground, water or ice. One of the methods to transform muon sea-level spectrum into depth one is to apply Monte Carlo technique which directly takes into account stochastical nature of energy loss. In order to decrease computation time down to acceptable level one has to use simplifications resulting in systematic errors which in some cases may distort result essentially. Here in this paper we present our analysis for dependence of computed depth muon flux upon the most important parameters of muon transport Monte Carlo algorithm which was done with the MUM (MUons+Medium) code. Contribution of different simplifications to the resulting error is considered, ranked and compared with uncertainties which come from parametrization accuracy both for sea-level muon spectrum and for muon cross sections.

hep-ph↗

arXiv2000

Atmospheric Muon Flux at Sea Level, Underground, and Underwater

The vertical sea-level muon spectrum at energies above 1 GeV and the underground/underwater muon intensities at depths up to 18 km w.e. are calculated. The results are particularly collated with a great body of the ground-level, underground, and underwater muon data. In the hadron-cascade calculations, the growth with energy of inelastic cross sections and pion, kaon, and nucleon generation in pion-nucleus collisions are taken into account. For evaluating the prompt muon contribution to the muon flux, we apply two phenomenological approaches to the charm production problem: the recombination quark-parton model and the quark-gluon string model. To solve the muon transport equation at large depths of homogeneous medium, a semi-analytical method is used. The simple fitting formulas describing our numerical results are given. Our analysis shows that, at depths up to 6-7 km w. e., essentially all underground data on the muon intensity correlate with each other and with predicted depth-intensity relation for conventional muons to within 10%. However, the high-energy sea-level data as well as the data at large depths are contradictory and cannot be quantitatively decribed by a single nuclear-cascade model.

hep-ph↗

arXiv1999

QCD-oriented nondiagonal GVDM

The nondiagonal generalized vector dominance model (GVDM) of photoabsorption is elaborated using QCD-motivated picture of the (gamma)-(q,anti q) - transition and subsequent meson dominated scattering of the (q, anti q)-pair on the nucleon. The relativistic constituent quark model for a description of the meson (q, anti q)-wave functionsis used. The meson-nucleon scattering is calculated in the two-gluon exchange approximation. It is shown that the destructive interference effects and corresponding cancellations in the photoabsorption cross section formula are small, so the GVDM predictions are incorrect if no extra cut-off factors in GVDM formulas are introduced.

hep-ph↗

arXiv1999

The QCD-Oriented Vector Dominance Model

The total photoabsorption cross section on the nucleon is studied using nondiagonal GVDM. Vector meson-nucleon scattering amplitudes are calculated in two-gluon exchange approximation of QCD. The off-diagonal transitions of diffraction dissociation type between different vector mesons and their contributions to the expression for the total photoabsorption cross section on the nucleon are also calculated. It is shown that destructive interference of diagonal and off-diagonal terms is not effective. The main conclusion is that a p-cut-off in gamma-quark antiquark transition is necessary for obtaining the convergence in the summation over all vector meson contributions.

hep-ph↗

arXiv1998

The Experimental Limits on Q-ball Flux with the Baikal Deep Underwater Array "Gyrlyanda"

Supersymmetric models allow for stable non-topological solitons, Q-balls, which can be produced in the early Universe and contribute to dark matter. Experimental signature of electrically neutral Q-balls is, in fact, the same as is expected for superheavy magnetic monopoles catalyzing baryon decay. Here we use the upper limits on monopole flux obtained with deep underwater Cherenkov array "Gyrlyanda" which operated in the Baikal lake in 1984-90 with 267 days of live time to obtain the limit on Q-ball flux. The last has been found to be equal to 3.9 x 10^{-16} cm^{-2} sr^{-1} s^{-1} (90% CL). This result is discussed and compared with other restrictions.

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